The present invention relates to an apparatus for tunneling holes through the ground, as for example air-operated impact devices for tunneling substantially horizontally for the purpose of laying cables or pipes beneath roadbeds or other surface structures.
This invention is related to my earlier U.S. Pat. No. 4,749,050, issued Jun. 7, 1988, which disclosed a tunneling apparatus having lubrication conduits for passing a supply of water to the forward end of the impact tool, thereby wetting the soil surrounding the forward end of the impact tool and reducing the impact resistance of the soil. The prior invention included an elongated outer housing threadably connected to a conically-shaped front tip, wherein the forward end of the front tip has a headpiece mounted thereon which has a discontinuous shoulder and neck section for providing an annular space about the front tip for injecting water. The headpiece has fluid outlets opening into this annular space, through which water or other liquids may be released to lubricate the front tip.
The present invention provides an improvement in the water conduits and outlets proximate the headpiece to increase the lubricating efficiency of the apparatus.